The utility of silanes, especially alkoxysilanes, as masonry water repellents is widely known. Compositions currently in use employ solutions of silanes in various organic solvents such as alcohol, e.g., U.S. Pat. Nos. 3,772,065 to Seiler and 4,342,796, to Brown et al., or hydrocarbons, e.g., Linn 4,525,213.
Aqueous silane compositions which are non-toxic and non-flammable have become important as effective masonry water repellent compositions, see U.S. Pat. Nos. 4,433,013 to Puhringer, 4,517,375 to Schmidt, 4,648,904 to DePasquale and Wilson (Re. 33,759), 4,877,654 to Wilson, 4,990,377 to Wilson, and 5,037,873 to Heaton. Aqueous siloxane compositions have also been used as masonry water repellents, see, U.S. Pat. Nos. 4,582,874 to Grape et al., and 5,091,002 to Schamberg et al.
While the performance of such aqueous compositions has been excellent in static water immersion tests with concrete cubes (see NCHRP No.244), they do not perform well in wind-driven rain tests such as ASTM E514-90. In such testing the pressurized water penetrates the water repellent outer layer of the masonry and seeps through.
Organopolysiloxane resins in solvent solutions have long been used for rendering masonry water repellent, see, U.S. Pat. Nos. 2,574,168 to Brick, 2,683,674 to Hafeber and Bunnell, 2,810,704 to Krantz, and 4,717,599 to Merrill. More recently water based organopolysiloxane resin emulsions for masonry water repellents have been developed, see, U.S. Pat. Nos. 4,175,159 to Raleigh, 4,525,502 to Traver, and 4,582,874 to Grape et al. A hydrophobic Silica was preferred in these formulations.
Organopolysiloxane resins are noted for their weatherability and they give an excellent water beading effect on masonry. Their drawbacks include a susceptibility to alkaline attack in concrete (esp. methylpolysiloxanes), relatively poor performance in static water immersion tests, and reduced permeability to moisture vapor versus organosilane and organosiloxane treatments. Also many substrates are discolored or darkened when they are treated with relatively low levels of some organopolysiloxane resins and organopolysiloxane oils.
Colloidal silica and fumed silica impart little or no sustained water repellency to masonry or wood, but when used in conjunction with other water repellents, they increase the stability of the formulations and/or improve the water beading characteristics of the treated masonry or wood, see, U.S. Pat. No. 4,209,432 to Roth. Recent water based formulations containing colloidal silica have been reported in U.S. Pat. Nos. 5,037,873 to Heaton and 5,091,002 to Schamberg, et al. A hydrophobic silica was preferred in these formulations.
It has now been found that water based formulations comprising hydrolyzable silanes and/or oligomers thereof, and/or organosiloxanes, in further combination with organopolysiloxane resins, and colloidal dispersions of filler particles, exhibit high effectiveness in retarding water penetration and leakage through porous substrates, particularly masonry. Testing reported hereinafter has shown that the time for pressure-driven water to penetrate masonry walls treated with the compositions of the present invention is vastly increased in comparison with walls treated with the compositions of the prior art, and further that the amount of water absorbed by the masonry treated with the compositions of this invention is greatly reduced.